CaMKII biophysics and its role in LTP

项目摘要 记忆是如何比编码它的分子的寿命更长的呢？二十多年前，弗朗西斯 克里克有先见之明地推测，也许一种多聚体蛋白质可以作为一种分子记忆， 通过亚基交换与新合成的蛋白质共享其活化状态，以储存 多年的记忆。Ca 2 +-钙调蛋白依赖性蛋白激酶II（CaMKII）被鉴定为一种酶， 符合这个描述例如，CaMKII在其功能关键位点的突变导致严重的学习 和记忆缺陷。CaMKII在阈值神经元尖峰频率下被激活，并且对长期的神经元放电至关重要。 增强作用（LTP）。理解LTP的一个主要障碍是缺乏对监管如何 在这种最初的高频刺激过程中招募的通路能够在面部保持持续的活跃 持续的蛋白质周转。我们最近的工作表明，CaMKII在 以激活依赖的方式激活全酶。重要的是，激酶活性被赋予未活化的 CaMKII全酶通过作为亚基交换的结果的反式磷酸化，从而增强 激活信号经过蛋白质降解的时间。这种循环可能会无限期地持续下去。我们的工作是 旨在进一步研究这一现象，特别是其在LTP中的作用。我们的主要研究 目的是：1）了解CaMK II独特的生物物理特性的作用（连接体长度如何影响 激活、频率依赖性和亚基交换），这有助于其成为“记忆”的潜力 分子，以及2）研究CaMK II的性质（如亚基交换和基因改变 表达），以确定其在LTP中的生理作用。这些具有挑战性的目标需要 从分子水平（蛋白质结构和调控）到细胞水平的信息合成 （哺乳动物细胞培养），最后到动物水平（转基因小鼠），这将是未来的研究。 完成拟议的工作将使我们能够更好地解决神经系统疾病的进展，因为它影响 记忆，如阿尔茨海默氏症，痴呆症和创伤性脑损伤中看到的病理。

PROJECT SUMMARY How does a memory outlast the lifetime of the molecule that encodes it? More than two decades ago, Francis Crick had the foresight to speculate that perhaps a multimeric protein could serve as a molecular memory by sharing its activation state with newly synthesized proteins through subunit exchange in order to store a memory for years. Ca2+-calmodulin dependent protein kinase II (CaMKII) was identified as an enzyme that may fit this description. For example, mutation of CaMKII at sites critical for its function results in severe learning and memory defects. CaMKII is activated at a threshold neuronal spike frequency and is crucial to long-term potentiation (LTP). A major obstacle to understanding LTP is the absence of understanding how regulatory pathways recruited during this initial high-frequency stimulus are able to remain persistently active in the face of ongoing protein turnover. Our recent work has shown that CaMKII exchanges subunits between holoenzymes in an activation-dependent manner. Importantly, kinase activity is conferred to unactivated CaMKII holoenzymes by trans-phosphorylation as a consequence of subunit exchange, thereby potentiating the activation signal past the time of protein degradation. This cycle may continue indefinitely. Our work is aimed to further investigate this phenomenon, specifically in respect to its role in LTP. Our major research goals are to: 1) understand the role of the unique biophysical properties of CaMKII (how linker length affects activation, frequency dependence and subunit exchange) that contribute to its potential for being a `memory molecule,' and 2) investigate the properties of CaMKII (such as subunit exchange and changes in gene expression) in cellular systems to determine its physiological role in LTP. These challenging goals require the synthesis of information obtained from the molecular level (protein structure and regulation) to the cellular level (mammalian cell culture) and finally to the animal level (transgenic mice), which will be for future study. Completion of the proposed work will allow us to better address neurologic disease progression as it affects memory, such as pathologies seen in Alzheimer's, dementia, and traumatic brain injury.